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    Subject[PATCH 5.15 258/277] tools build: Filter out options and warnings not supported by clang
    Date
    From: Arnaldo Carvalho de Melo <acme@redhat.com>

    commit 41caff459a5b956b3e23ba9ca759dd0629ad3dda upstream.

    These make the feature check fail when using clang, so remove them just
    like is done in tools/perf/Makefile.config to build perf itself.

    Adding -Wno-compound-token-split-by-macro to tools/perf/Makefile.config
    when building with clang is also necessary to avoid these warnings
    turned into errors (-Werror):

    CC /tmp/build/perf/util/scripting-engines/trace-event-perl.o
    In file included from util/scripting-engines/trace-event-perl.c:35:
    In file included from /usr/lib64/perl5/CORE/perl.h:4085:
    In file included from /usr/lib64/perl5/CORE/hv.h:659:
    In file included from /usr/lib64/perl5/CORE/hv_func.h:34:
    In file included from /usr/lib64/perl5/CORE/sbox32_hash.h:4:
    /usr/lib64/perl5/CORE/zaphod32_hash.h:150:5: error: '(' and '{' tokens introducing statement expression appear in different macro expansion contexts [-Werror,-Wcompound-token-split-by-macro]
    ZAPHOD32_SCRAMBLE32(state[0],0x9fade23b);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    /usr/lib64/perl5/CORE/zaphod32_hash.h:80:38: note: expanded from macro 'ZAPHOD32_SCRAMBLE32'
    #define ZAPHOD32_SCRAMBLE32(v,prime) STMT_START { \
    ^~~~~~~~~~
    /usr/lib64/perl5/CORE/perl.h:737:29: note: expanded from macro 'STMT_START'
    # define STMT_START (void)( /* gcc supports "({ STATEMENTS; })" */
    ^
    /usr/lib64/perl5/CORE/zaphod32_hash.h:150:5: note: '{' token is here
    ZAPHOD32_SCRAMBLE32(state[0],0x9fade23b);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    /usr/lib64/perl5/CORE/zaphod32_hash.h:80:49: note: expanded from macro 'ZAPHOD32_SCRAMBLE32'
    #define ZAPHOD32_SCRAMBLE32(v,prime) STMT_START { \
    ^
    /usr/lib64/perl5/CORE/zaphod32_hash.h:150:5: error: '}' and ')' tokens terminating statement expression appear in different macro expansion contexts [-Werror,-Wcompound-token-split-by-macro]
    ZAPHOD32_SCRAMBLE32(state[0],0x9fade23b);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    /usr/lib64/perl5/CORE/zaphod32_hash.h:87:41: note: expanded from macro 'ZAPHOD32_SCRAMBLE32'
    v ^= (v>>23); \
    ^
    /usr/lib64/perl5/CORE/zaphod32_hash.h:150:5: note: ')' token is here
    ZAPHOD32_SCRAMBLE32(state[0],0x9fade23b);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    /usr/lib64/perl5/CORE/zaphod32_hash.h:88:3: note: expanded from macro 'ZAPHOD32_SCRAMBLE32'
    } STMT_END
    ^~~~~~~~
    /usr/lib64/perl5/CORE/perl.h:738:21: note: expanded from macro 'STMT_END'
    # define STMT_END )
    ^

    Please refer to the discussion on the Link: tag below, where Nathan
    clarifies the situation:

    <quote>
    acme> And then get to the problems at the end of this message, which seem
    acme> similar to the problem described here:
    acme>
    acme> From Nathan Chancellor <>
    acme> Subject [PATCH] mwifiex: Remove unnecessary braces from HostCmd_SET_SEQ_NO_BSS_INFO
    acme>
    acme> https://lkml.org/lkml/2020/9/1/135
    acme>
    acme> So perhaps in this case its better to disable that
    acme> -Werror,-Wcompound-token-split-by-macro when building with clang?

    Yes, I think that is probably the best solution. As far as I can tell,
    at least in this file and context, the warning appears harmless, as the
    "create a GNU C statement expression from two different macros" is very
    much intentional, based on the presence of PERL_USE_GCC_BRACE_GROUPS.
    The warning is fixed in upstream Perl by just avoiding creating GNU C
    statement expressions using STMT_START and STMT_END:

    https://github.com/Perl/perl5/issues/18780
    https://github.com/Perl/perl5/pull/18984

    If I am reading the source code correctly, an alternative to disabling
    the warning would be specifying -DPERL_GCC_BRACE_GROUPS_FORBIDDEN but it
    seems like that might end up impacting more than just this site,
    according to the issue discussion above.
    </quote>

    Based-on-a-patch-by: Sedat Dilek <sedat.dilek@gmail.com>
    Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # Debian/Selfmade LLVM-14 (x86-64)
    Cc: Adrian Hunter <adrian.hunter@intel.com>
    Cc: Fangrui Song <maskray@google.com>
    Cc: Florian Fainelli <f.fainelli@gmail.com>
    Cc: Ian Rogers <irogers@google.com>
    Cc: Jiri Olsa <jolsa@kernel.org>
    Cc: John Keeping <john@metanate.com>
    Cc: Leo Yan <leo.yan@linaro.org>
    Cc: Michael Petlan <mpetlan@redhat.com>
    Cc: Namhyung Kim <namhyung@kernel.org>
    Cc: Nathan Chancellor <nathan@kernel.org>
    Cc: Nick Desaulniers <ndesaulniers@google.com>
    Link: http://lore.kernel.org/lkml/YkxWcYzph5pC1EK8@kernel.org
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    tools/build/feature/Makefile | 7 +++++++
    tools/perf/Makefile.config | 3 +++
    2 files changed, 10 insertions(+)

    --- a/tools/build/feature/Makefile
    +++ b/tools/build/feature/Makefile
    @@ -216,6 +216,13 @@ PERL_EMBED_LIBADD = $(call grep-libs,$(P
    PERL_EMBED_CCOPTS = `perl -MExtUtils::Embed -e ccopts 2>/dev/null`
    FLAGS_PERL_EMBED=$(PERL_EMBED_CCOPTS) $(PERL_EMBED_LDOPTS)

    +ifeq ($(CC_NO_CLANG), 0)
    + PERL_EMBED_LDOPTS := $(filter-out -specs=%,$(PERL_EMBED_LDOPTS))
    + PERL_EMBED_CCOPTS := $(filter-out -flto=auto -ffat-lto-objects, $(PERL_EMBED_CCOPTS))
    + PERL_EMBED_CCOPTS := $(filter-out -specs=%,$(PERL_EMBED_CCOPTS))
    + FLAGS_PERL_EMBED += -Wno-compound-token-split-by-macro
    +endif
    +
    $(OUTPUT)test-libperl.bin:
    $(BUILD) $(FLAGS_PERL_EMBED)

    --- a/tools/perf/Makefile.config
    +++ b/tools/perf/Makefile.config
    @@ -788,6 +788,9 @@ else
    LDFLAGS += $(PERL_EMBED_LDFLAGS)
    EXTLIBS += $(PERL_EMBED_LIBADD)
    CFLAGS += -DHAVE_LIBPERL_SUPPORT
    + ifeq ($(CC_NO_CLANG), 0)
    + CFLAGS += -Wno-compound-token-split-by-macro
    + endif
    $(call detected,CONFIG_LIBPERL)
    endif
    endif

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